Saturday, 28 January 2012

Clocks make you fit, evolutionarily speaking

Yesterday I attended the Bitesize lunchtime lectures at UCL and once again really enjoyed both the talks. Andy Beale gave a great introduction to the body clock field and his own research using a blind cavefish to investigate the evolutionary importance of body clocks.

This was Andy's first public engagement lecture at UCL. His intro "why we should care about body clocks" had photos of Andy himself sleeping (sleep-wake cycle), in a plane (jet lag), and drinking alcohol at lunchtime (which will get you more drunk than in the evening). The audience were laughing and certainly engaged.

Andy uses jet lag as an example of how we can disrupt our body clock (C) Andrew Beale, 2012

Andy gave examples of many other species that have body clocks, from the parasite that causes malaria, to the sleeping lion. Andy's interest in body clocks stems from his interest in evolution, what is so advantageous about having a body clock that it would be found so universally in so many diverse creatures? Does the early bird catch the worm?

Evolution is driven by natural selection, Darwin's "survival of the fittest", and in this instance it can be concluded that "clocks make you more fit". Being able to predict the sunrise and sunset might make you more likely to catch your prey/avoid your predator, and therefore your likelihood of survival.

Andy is researching a cave-dwelling fish from Mexico, that has been isolated in caves for more than a million years, with no access to sunlight, and no knowledge of "time of day". Have these cavefish kept a body clock, which would be redundant in their natural environment?

One unusual advantage of these Mexican cavefish is in the surrounding rivers another surface-dwelling river fish can be found, which do see daylight. These sighted river fish have the same ancestor as the cave fish (before they went into the caves) so make a vital comparison.

A blind Mexican cavefish next to two river fish. They have the same common ancestor and apart from a lack of eyes and skin colour are still remarkably similar so can be used to study evolution. Credit to Richard Borowsky

A lot of Andy's research has looked at gene expression. To convey what this means he used an excellent analogy. If we think of DNA as book, and genes as words, gene expression is like speaking the words aloud.

Andy's results from the cavefish show that when put on an artificial day in the lab aquaria with light and dark cycles, their genes act like the river fish, with a body clock. However, when in constant darkness, like in the cave, they lose their rhythmicity, they are not using their clock. His conclusions so far suggest that despite cavefish keeping their clock, in their normal environment the clock is not active.

Questions from the audience asked whether there were any animals that were found in the wild kept in constant lightness. Andy had mentioned that at the poles animals might be exposed to constant light for certain periods of the year, but not throughout the year. Andy theorized that it might be possible on another planet, and that would be interesting to look at.